When several circuit breakers are working in parallel, there may be a requirement to interlock two breakers so that when one is being turned ON, the other is turned OFF, so that only one may be closed (ON) at a time.
There are three most common types of mechanical interlocks: the walking beam, the sliding bar and the key interlock. The sliding bar interlock is typified by U.S. Pat. Nos. 4,516,100; 4,295,053 and 4,286,242. Typical of the walking beam interlock is U.S. Pat. No. 3,710,288. As illustrated, for instance, in U.S. Pat. Nos. 4,286,242 and 4,516,100, the sliding bars control reciprocal plungers which connect with corresponding control members of the parallel circuit breakers so that when one control member is brought to the closed position (ON), the other control member is automatically pulled away by its associated plunger toward the open position (OFF). In U.S. Pat. No. 3,710,188 is described a lever pivoting centrally with its two ends achieving the same opposite ON and OFF positions for a contactor. The same result could be obtained through a plunger at each of these two ends. The plungers have been shown in U.S. Pat. Nos. 4,516,100; 4,286,242 and 4,295,053 engaging directly the moveable contact carrier or moveable arm of the circuit breaker. Indeed, the plungers may be interfaced instead with the crossbar arm which, in a circuit breaker, is known to cause the moveable contact arm to be moved to the closed (ON) or to the open (OFF) position.
The present invention relates to initially adjusting the interlock walking beam of a circuit breaker so as to provide an exact and opposite relationship between ON and OFF positions, once the opposite circuit breakers are operating in parallel. This problem has been considered in U.S. Pat. No. 3,710,288, considering a mechanical interlock in the context of the operation of reversible speed motors controlled by contactors which should not be actuated simultaneously. The problem considered here has to do with adjusting a mechanical interlock on a back panel, or control board, between contactors of different size and/or manufacturers. Adjustment means are provided for compensating for different thicknesses or irregularities, or for tolerances, in the mounting surfaces. In this regard, the '288 patent shows the use of a bracket with slots and several screws which allow positioning of the lever and setting the central pivot at the proper distance relative to the operating contacts to be actuated upon at both ends of the lever. The present invention proposes a simpler mounting of the walking beam, and calls for a single screw adjustment, by the operator, of a walking beam associated with parallel circuit breakers, or contactors.